Timing advance for non-terrestrial network communication

Abstract

Methods, systems, and devices for addressing timing advance (TA) in non-terrestrial network communication is disclosed herein. A wireless transmit and receive unit (WTRU) may receive system information from a base station attached to an airborne or spaceborne vehicle that indicates a physical random access channel (PRACH) resource. The WTRU may determine a timing offset based on a plurality of information, such as the location information and the system information. The WTRU may transmit a preamble using the timing offset via the PRACH resource. The base station may receive the preamble and send a random access response (RAR) that includes, for example, a TA command. The WTRU may receive the RAR including the TA command and combine the timing offset with the TA command to determine an actual TA, after which the WTRU may use the actual TA for uplink transmissions.

What is claimed is: 
     
       1. A method performed by a wireless transmit and receive unit (WTRU), the method comprising:
 receiving, from a spaceborne communications satellite, system information that includes a position of, and trajectory parameters, including velocity, about, the spaceborne communications satellite; 
 determining a position of the WTRU using a global navigation satellite system (GNSS); 
 estimating a propagation delay based on the determined WTRU position and the position of, and the trajectory parameters about, the spaceborne communications satellite; 
 determining a timing advance (TA) based on the estimated propagation delay; and 
 transmitting a signal using the determined TA. 
 
     
     
       2. The method of  claim 1 , wherein the system information indicates one or more physical-random-access-channel (PRACH) resources. 
     
     
       3. The method of  claim 2 , further comprising:
 receiving a random-access response (RAR), wherein the RAR includes a timing-advance (TA) command; 
 determining an adjusted TA based on the TA command and the estimated propagation delay; and 
 transmitting a message using the adjusted TA. 
 
     
     
       4. The method of  claim 3 , wherein the RAR further includes at least one of a power correction, an uplink grant, or a temporary identifier. 
     
     
       5. The method of  claim 3 , wherein the RAR includes a two-part bitfield, wherein a first part of the two-part bitfield has a high-resolution TA and a second part of the two-part bitfield has a low-resolution TA. 
     
     
       6. The method of  claim 1 , wherein the transmitting a signal occurs at a random-access-channel (RACH) opportunity indicated in the system information. 
     
     
       7. The method of  claim 1 , wherein the spaceborne communications satellite comprises a relay satellite. 
     
     
       8. A wireless-transmit-and-receive unit (WTRU), comprising a processor coupled to a transceiver, the processor and transceiver configured to:
 receive, from a spaceborne non-navigation satellite, system information that includes a position of, and trajectory parameters, including velocity, about, the spaceborne non-navigation satellite; 
 determine a position of the WTRU using a global navigation satellite system (GNSS); 
 estimate a propagation delay based on the determined WTRU position and the position of, and the trajectory parameters about, the spaceborne non-navigation satellite; 
 determine a timing advance (TA) based on the estimated propagation delay; and 
 transmit a signal using the determined TA. 
 
     
     
       9. The WTRU of  claim 8 , wherein the system information indicates one or more physical-random-access-channel (PRACH) resources. 
     
     
       10. The WTRU of  claim 9 , the processor and transceiver further configured to:
 receive a random access response (RAR), wherein the RAR includes a timing-advance (TA) command; 
 determine an adjusted TA based on the TA command and the estimated propagation delay; and 
 transmit a message using the adjusted TA. 
 
     
     
       11. The WTRU of  claim 10 , wherein the RAR further includes at least one of a power correction, an uplink grant, or a temporary identifier. 
     
     
       12. The WTRU of  claim 10 , wherein the RAR includes a two-part bitfield, wherein a first part of the two-part bitfield has a high-resolution TA and a second part of the two-part bitfield has a low-resolution TA. 
     
     
       13. The WTRU of  claim 8 , wherein the transmitting a signal occurs at a random-access-channel (RACH) opportunity indicated in the system information. 
     
     
       14. The WTRU of  claim 8 , wherein the system information further includes timing information. 
     
     
       15. The WTRU of  claim 8 , wherein the spaceborne non-navigation satellite is configured to relay signals between the processor and transceiver and a device remote from the processor and transceiver.